NO314862B1 - Auto-telescopic display with pixel matrix and optical system, as well as related micro lens applications - Google Patents

Abstract

In the case of an automoscopic, for example autostereoscopic screen, with a pixel / pixel matrix (12,14,16,18) and which is assigned to a lens system, the aim has been to expand the limits of the screen's automulti / autostereocopic quality properties, and for this purpose, the lens system comprises partly an array of microlenses, one for each pixel (12, 14, etc.), partly a lenticular lens / macro lens (20). with a curved focus plane (20A). The microlenses are arranged to project light from LEDs via the pixels of the screen in the matrix on the curved focus plane (20A) of the lenticular lens (20).

Description

AUTOMULTISCOPIC DISPLAY WITH PICTURE ELEMENT MATRIX AND

OPTICAL SYSTEM AND RELATED MICRO LENS APPLICATIONS

The present invention relates to an automultiscopic screen which contains image elements arranged in lines and columns of an image matrix and which otherwise exhibits features in accordance with the introductory part of patent claim 1.

Likewise, the invention relates to special applications of microlenses and similar light-shaping bodies which are technically functionally equivalent thereto and can focus, shape and bend light according to different, predetermined light beam patterns. In addition to refraction and reflection, there is also diffraction to shape light. Diffraction uses the wave properties of light to create light patterns through interference. There are diffractive lenses which can advantageously be inserted into or in connection with an automultiscopic screen according to the invention instead of, for example, microlenses.

Optical systems included in arrangements according to the invention can thus include refractive lenses or diffractive lenses (for example diffractive lenses with double wavelength which can take two wavelengths and focus them on the same focal plane). Diffractive lenses do not bend light in the traditional sense, but form interference patterns.

The invention includes any automultiscopic screen with picture element matrix, for example an autostereoscopic screen, and said optical system, which may consist of a lens system, generally includes light-shaping devices, including microlenses. The said special applications of these light-forming organs/microlenses thereby constitute applications which can be considered special, but related to their tasks in connection with said autoscopic screen's image elements.

An LCD screen is a type of screen to which the invention can be applied, for example an autostereoscopic LCD screen where its depth/spatial effect or perspective/three-dimensional effect is provided by means of said optical system in the form of a suitable lens system.

The term "lens" can therefore in this context include, among other things, translucent, light-refracting bodies bounded by surfaces of which at least one has a curved design, as there are spherical/aspherical lenses. Diffractive lenses can be used in cases where the underlying image element/pixel consists of three distinct color components, red, green and blue. "Resolution" in relation to automulti-/autostereoscopic displays of the type in question is defined as the pixel density on the screen (or on a photograph).

Automultiscopy/stereoscopy provided by means of lenses over a flat screen represents known technology, cf. WO 99/00993 and U.S. Pat. patent no. 6,064,424, both of which constitute illustrative and representative examples of the state of the art.

WO 99/00993 deals with an autostereoscopic screen, as this patent publication discusses a broad spectrum within known autostereoscopy.

US 6,064,424 deals with an autostereoscopic screen display device, and mentions attempts where, in connection with the device's screen, one has tried to utilize vertical resolution in the horizontal direction using classic lens technology. It is disadvantageous with this known stereoscopic display device that an upscaling/enlargement of an image or parts of the image cannot be carried out here.

GB 2 272 555 describes a stereoscopic projector where the image-forming device is built up in layers from first a row of lenses, then a light modulator, then a diffusing layer and finally a second row of lenses closest to the observer. In addition, the document describes a light source row before the first row of lenses. The diffusing layer is placed in the focal plane of the second row of lenses closest to the observer, as well as at an image-forming plane in relation to the first row of lenses.

EP 0809 124 describes a diffractive/refractive lens matrix. The lens array is used to focus light onto a photosensitive array of sensors. For each lens element, the optical axis is specified as a function of the radial position of the lens element. The lenses are concave. WO 99/00993 deals with an autostereoscopic screen, as this patent publication discusses a broad spectrum within known autostereoscopy. Said known technique, where autostereoscopy is created and maintained over a flat screen with the help of lenses, has basic physical limitations. Due to the properties of light waves, there is a lower limit to the number of image elements (pixels) that can be placed behind a lens of the kind included in a typical autostereoscopic lens system, and thus also to the number of angles (in space) that can be displayed. This in turn places fundamental limitations on how good autostereoscopic reproduction and thus the experience that traditional lens systems will be able to provide.

A lens system that can be used as an optical system for said screen can advantageously constitute a special case of a kind of optical system that is shown and described in several patent documents in connection with so-called "infinity displays" ("infinite display" or "infinite optical image-forming apparatus"; cf. for example US 3,443,858 and 4,653,875).

Such infinity screens exhibit properties that make an image located close to an observer appear to be (approximately) infinitely far away. This principle is used, among other things, in flight simulators associated with the American air force, to create more realistic conditions.

Technically, an infinity screen can be defined as a screen that focuses an image (approximately) towards "infinity".

If a user looks at such a screen from the front, he/she will see the entire image in question as if it were infinitely far away. This means that if you stand (almost) infinitely far away from such an infinity screen, the entire screen will be covered by only one color, which is a function of the angle from which the screen is viewed. One can therefore build up an autostereoscopic screen by combining many such infinity screens as "picture elements/pixels" in a larger macro screen.

A primary purpose of the present invention has therefore been to avoid shortcomings and disadvantages of known technology, as well as to expand the limits of automulti-/autostereoscopic screens with regard to the depth effect reproduction/spatial effect experience.

A further purpose is to cancel or to a significant extent reduce the above-mentioned limiting factors that have a negative effect on the achievement of the invention's actual purpose, namely a significant improvement of the automulti-/autostereoscopic experience that an optical system, for example a lens system, will be able to give via the screen.

According to the present invention, said purpose is to be realized with optimally simple and, moreover, relatively cheap means. In addition, it is intended to maintain a long service life for the screen, light-forming organs/lenses and associated components. Known stereoscopic screens and screen display devices and apparatuses exhibit certain properties which experience has shown to be advantageous in more subordinate respects. It may be appropriate to retain such advantageous features of known technology, as long as this can be ensured without weakening the primary features of the automulti-/autostereoscopic screen according to the invention and which ensures the solution of the defined task.

Said purpose is achieved by the fact that an automultiscopic screen of the type specified in the introductory part of patent claim 1 is additionally designed and arranged in accordance with the specifications that appear in the characterizing part of patent claim 1.

According to the invention, the above-mentioned main purpose is realized in that said optical system comprises partly a matrix of light-shaping elements, one for each image element in the screen matrix, and partly a macro-optical element with a focal plane, which light-shaping elements are arranged to project light from the screen's image elements onto the focal plane of macro-optic elements.

The limitations associated with how good an automulti-/autostereoscopic experience that traditional optical systems/lens systems are able to provide can, according to the invention, be removed or significantly reduced by projecting all or parts of the screen's vertical resolution onto the horizontal direction, as specified in patent claim 1.

If one utilizes the entire vertical resolution in the horizontal direction, the number of unique angles in the horizontal direction will be squared, which means that 2 x 2 angles become 4x1 angles, 10 x 10 angles become 100 x 1 and so on.

In other words, the invention can thus be said to consist of using the vertical resolution on, for example, an LCD screen (liquid crystal display = screen with liquid crystals; other screens are, for example, OLED, "organic light emitting display" or LEP, "light emitting polymer ") in the horizontal direction. The eyes in a pair of eyes are normally located in a common horizontal plane, and it is therefore most appropriate to ensure good angular resolution in that direction.

According to the invention, this is implemented by inserting light-forming organs, preferably in the form of specially shaped microlenses, and placing them in front of the individual image elements (pixels) on the LCD screen. These specially shaped microlenses stretch, compress and bend the light from the individual picture elements. The microlenses thereby provide such light deflection that, for example, a 2x2 matrix of image elements (pixels) can be converted into a 4x1 matrix. A matrix is thereby defined as a rectangular array of elements, here image elements, arranged in rows and columns that can be processed according to the rules of matrix algebra.

Expressed more generally, the use of said microlenses according to the invention results in a transformation of an AxB image element matrix into an (A<*>B)xl image element matrix, which corresponds to an increase of the angular resolution in the horizontal direction. The use of microlenses according to the invention can result in the transformation of a flat image element matrix into a curved image element matrix that coincides with the lens system's curved focal plane which creates the holographic effect, in order to reduce the complexity of the holographic lens system.

An N x M pixel matrix can be transformed into any p x q matrix, where p<*>q = N<*>M.

Within the framework of the invention, the entire vertical resolution of the screen can be used in the horizontal direction, but it is also possible and advantageous to make partial use of the vertical resolution of an LCD screen in the horizontal direction. It is thus, for example, entirely possible to transform a 16x16 matrix into, for example, a 32x8 matrix.

Once one has come to the realization that in the context of the invention it is generally advantageous to design special microlenses for each individual image element in the screen, this opens up possibilities that would otherwise not have been available.

Since you first have to bend and stretch the light from the individual image elements, there is no additional cost, including shaping the light in such a way that it is projected onto the curved focal plane of the macro lens, which leads to a far better viewing angle than you would otherwise have achieved.

Within traditional optics (for example in photography devices), the focal plane of the lenses is an important issue that must be managed. A simple lens has a curved focal plane, but

as a rule, it is desirable that the focal plane is flat, because the film in the cameras in question lies flat; an LCD screen in a projector is flat, etc. By using a series of lenses through which the light must travel, the focal plane can be straightened.

This in and of itself can work very well, but inevitably brings with it the disadvantage that the complexity of the lens system increases, and the device becomes more expensive than it would have been with a simple lens. Not least, this situation will have negative consequences in the case of a holographic screen where there may be a need for several thousand lens systems of this kind.

According to one preferred embodiment, the invention broadly comprises six functional elements, (i) screen, (ii) image element matrix (in the screen), (iii) matrix of light-shaping devices, typically consisting of microlenses, one for each image element, (iv) curved/flat focal plane, (v) light-shaping and diffusing membrane on the focal plane, and (vi) lenticular lens (macro lens) which creates a so-called holographic effect. Holography is explained in more detail in the special part of the description with reference to the attached drawings. All components are not critical for carrying out the task of the invention. Thus, for example, the light-shaping and diffusing membrane on the focal plane is part of an eventual feature in a combination of known, known in and of itself and new detail features of an automulti-/autostereoscopic screen of the type in question.

The microlenses in the matrix (iii) which constitute the light-shaping devices, but which can be replaced with other, functionally equivalent organs/devices, project the light from the picture elements in the picture element matrix (ii) onto the curved/flat focal plane of the lenticular lens (vi) [the macroscopic element] (iv). This focal plane (iv) can be covered by said light-shaping and diffusing film (v) which diffuses the light from the image elements and spreads it in all directions towards said lenticular lens (vi) which emits the light from the individual image elements in the desired direction.

Some terms that are repeated in this patent formulation are defined as follows: Stereoscopy is previously defined; autostereoscopy is an expression of a stereoscopic effect that is established without the use of polarized glasses or similar aids.

As the present invention allows for an arbitrary number of unique angles, the display is more related to automultiscopy than to autostereoscopy.

Screen resolution has previously been defined and is typically stated in megapixels or in horizontal x vertical resolution.

Image element size is the size of an image element (pixels); in typical cases corresponding to 0.25 mm on an LCD screen.

Angular resolution indicates the number of unique angles on an automultiscopic screen and is stated in the total number of angles or in horizontal x vertical resolution, angle size is the size of the angle between two unique images from the automulti/autostereoscopic screen. An angle size of 0.1° or less will provide a very realistic automulti/autostereoscopic experience. Viewing angle specifies the angular range where the display is automulti-/autostereoscopic.

Minimum eye distance is here defined as the distance between the eyes in a pair of eyes. In an adult, this mini-small eye distance corresponds to approx. 5 cm, and in a child to approx. 3 cm. Screen distance is the distance between the pair of eyes and the screen.

Pixel angle indicates the angular size of a picture element, which is mathematically defined as atan (pixel size: screen distance). The maximum pixel angle is the largest acceptable pixel angle, which should not be greater than 0.05°. The eyes are not able to perceive pixel angles (angles on picture elements) that are smaller than 0.01°, so that this angle never needs to fall below this value.

Minimum distance indicates the smallest screen distance that gives an acceptable pixel angle (angle of image element). Minimum distance is defined here as the distance one must be from an autostereoscopic screen for the pixel angle to have a maximum value. If you are at a shorter distance from the screen, the image will start to look grainy. Minimum distance is defined mathematically as pixel size : tan (maximum pixel angle). Maximum distance corresponds to the largest screen distance where it is still possible to view the screen autostereoscopically, and is defined mathematically as the ratio between eye distance and tan (angular size).

Range is defined here as the ratio between maximum distance and minimum distance. As a general principle, it is desirable to have as little range as possible.

In a preferred embodiment, said optical system can advantageously consist of a lens system whose matrix of light-forming organs has the form of a microlens matrix, said macro-copic element having the form of a macrolens/lenticular lens, which exhibits a curved focal plane. The microlenses are designed to project light from the screen's picture elements onto the curved focal plane of said lens.

In the subsequent special description where a concrete embodiment is explained, the more specific terms will generally be used, such as microlenses instead of the more comprehensive expression "light-forming organs", macrolenses instead of "macro-optical element", autostereoscopic instead of "automultiscopic" and so on.

Reference is made to accompanying drawings which illustrate representative examples of the invention's execution and use in the form of schematically produced, non-limiting embodiments; and where: Fig. 1 shows a perspective view of a specially shaped microlens used in a lens system for an autostereoscopic LCD screen according to the invention; Fig. 2 shows a simplified schematic representation which seeks to visualize the placement of a microlens in front of the individual picture elements on the LCD screen, where, among other things, a deflection of light from LEDs is implemented; Fig. 3 illustrates a deflection of light from light-emitting diodes by means of microlenses in such a way that a 2x2 matrix of picture elements is converted into a 4x1 matrix; Fig. 4 shows an example of an application of microlenses to focus the light from the picture elements on the curved focal plane of the large lens which creates the holographic effect; Fig. 5 schematically illustrates certain parameters that are in relation to each other, the parameters here being image element, screen distance, angle of image element (pixel angle) and size of image element (pixel size); Fig. 6 shows a similar schematic presentation of parameters that are in relation to each other, namely viewing area, maximum distance, viewing angle, screen, minimum distance and angular size; Fig. 7 and 8 are intended to illustrate the difference between an ordinary photograph (Fig. 7) which looks the same from all viewing angles and a hologram (Fig. 8) which, when turned, creates the illusion that the image rotates; Fig. 9 and 10 are intended to illustrate the difference between an ordinary photograph (Fig. 9) and a hologram (Fig. 10) as representative of a type of holographic system; Fig. 11 illustrates in a highly schematic representation a lens system in connection with a flat screen where the lenses create autostereoscopy in accordance with known technology; Fig. 12 illustrates in a corresponding presentation form how all or parts of the vertical resolution can be projected over in the horizontal direction, in order to avoid the limitations associated with the flat screen and assigned lens system according to fig. 11; and Fig.13 finally illustrates side-by-side lenses which aim to flatten a curved focal plane, thereby increasing the complexity of the system, while an important purpose of the present invention consists in reducing the complexity of the lens system without loss of viewing angle by projecting the image elements onto a single lens' curved focal plane; Fig. 14A-14C schematically show microlenses with mutually different shapes on the lens body, respectively designed with curvature (Fig. 14A) for focusing the light, with tilt (Fig. 14B) for deflection of the light, and with curvature and tilt (Fig. 14C ) for focusing and deflection of the light [if you want different deflection/tilt in the X and Y directions, the respective lens must be designed accordingly, that is, with deviant deflection/tilt in the aforementioned coordinate directions].

In the subsequent special description of the automulti-/autostereoscopic screen, the components included in the screen display construction and their schematically visible functional features, reference is first made to fig. 1-4, where fig. 1 shows a perspective view of a specially designed microlens 10. In the embodiment shown, the microlens 10 has an irregular shape made up of six different surfaces, five flat outer surfaces with mutually deviating shapes and one curved surface 10a whose opposite flat surface is denoted by 10b. The geometric shape of this microlens 10 is without a plane of symmetry.

Such microlenses 10 are in a predetermined number placed in front of an LCD screen (not shown) individual image elements,

one for each picture element, to stretch, compress and bend light originating from individual picture elements as shown strongly schematically in fig. 2, where the arrow A denotes the direction of conversion, and where the light is bent so that a square image element 12 is converted via its microlens into an elongated rectangular image element 12a with the long sides in the height direction in the drawing figure.

Fig. 3 illustrates a to fig. 2 corresponding case, where the light from the LEDs (not shown) via microlenses according to the invention is deflected so that a matrix of 2x2 picture elements / pixels 12, 14, 16, 18 is converted (see arrow A) into a 4x1 pixel matrix with tall, narrow picture elements 12a, 14a, 16a, 18a.

According to the invention, specially shaped microlenses 10, fig. 1, one for each individual image element associated with the stereoscopic screen display technique. This use of microlenses facilitates the conditions and opens up new possibilities, especially in relation to the focal plane of the lenses in related optics.

A simple lens 20, fig. 4, has a curved focal plane 2OA.

As mentioned at the beginning, however, it is often desirable that the focal plane is flat and level. Straightening a curved focal plane represents in and of itself known technique, but known measures inevitably result in complex lens systems and correspondingly expensive stereoscopic devices etc. This problem is particularly acute with holographic screens where such screen alignment will require thousands of such lens systems .

In order to solve this screen alignment problem without thereby giving rise to new, other problems, according to the invention, microlenses 10 are arranged to focus the light from the picture elements 12, 14, 16, 18 on the curved focal plane 20A of the large lens 20. This creates a holographic effect, fig. 4.

The focal plane 2OA of the macro lens (the lenticular lens) has a (not shown) light-shaping, diffusing membrane which diffuses the light from the image elements 12, 14, 16, 18 and spreads it in all directions towards the lenticular lens 20 which is a large lens with a typical lens shape, that is to say, with a straight, regular shape formed by two mirror-symmetric, in opposite directions convex lens body halves, where said plane of symmetry is square, see fig. 4.

The large lens 20 sends received light out in the desired direction.

The autostereoscopic screen according to the invention can be said to comprise the following functional components in most forms of Iseformer: (i) screen, (ii) pixel matrix [in the screen (i)], (iii) matrix of light-shaping devices in the form of microlenses 10, one for each image element/pixel, (iv) curved focal plane (20A), light-shaping and diffusing membrane (without reference number) on the focal plane 20A, as well as the macro lens/lenticular lens 20 which creates the aforementioned holographic effect. The microlenses (not shown in Fig. 4) project the light from the image elements 12, 14, 16, 18 onto the curved focal plane 2OA of the lenticular lens 20 (which is covered by said light-shaping, diffusing film - not shown).

This membrane diffuses the light from said image elements and spreads it in all directions towards the macro lens 20, which sends the received light out in the desired direction.

The present invention is thus related to two related aspects: (a) the use of microlenses 10 to transform an AxB image element matrix into an (A<*>B)xl image element matrix, with the intention of increasing the angular resolution in the horizontal direction (the vertical resolution of an LCD screen is used in the horizontal direction, as one does not need to use the entire vertical resolution in the horizontal direction, as it is entirely possible to transform a 16x16 pixel matrix into, for example, a 32x8 pixel matrix); (b) using microlenses to transform a flat/planar pixel array into a curved pixel array that coincides with the curved focal plane of the lens 20 or lens system producing the holographic effect, in order to reduce the complexity of the holographic lens system.

As one must still stretch and bend the light from the individual image elements with the help of a specially shaped microlens assigned to each image element, the subject matter of the invention does not represent any additional cost at the same time to shape the light in such a way that it is projected onto the curved focal plane 20A of the macrolens 20, whereby you achieve a far better angle of view than you would otherwise have been able to get.

A phenomenon called holography, for example in connection with an autostereoscopic screen with high horizontal angular resolution, can be explained as follows: An ordinary photograph is distinguished by looking the same regardless of the angle from which it is viewed, see fig. 7. This is because every point in the image emits light of the same color in all directions, that is to say that an example red point in the photograph will look red regardless of where it is viewed from, see fig. 9.

In fig. 5 and 6 are highly schematically produced one eye 0 and two eyes 0 respectively in relation to an image element 22, fig. 5, whose pixel size is denoted by 24, while the screen distance is denoted by 26 and the pixel angle by 28.

In fig. 6, the reference number 30 denotes a screen where the field of view is delimited between arcs representing respectively the maximum distance 34 and the minimum distance 36, as well as in relation to the screen's 30 symmetry plane "radial" limitation lines 38 and 40 for the viewing angle 42. The angle size is marked at 44. The field of view is in fig. 6 denoted by 46.

In a holographic system, for example in the form of a hologram, it is characteristic that one sees different images from different angles, which is due to the fact that each point emits different light in different directions, see fig. 10, where the arrows from left to right could have the following colours: orange, blue, red, yellow, green, black, red, while all the arrows in fig. 9 indicates that the point has the same color regardless of the "radiation angle".

In a hologram, the colors from each point at all angles are put together in such a way that they simulate the light from objects in the room. When you turn a hologram (fig. 8 and 10), the illusion is thus created that an object is rotated, fig. 8, which gives an experience of depth effect. A teapot in the photograph in fig. 7 looks identical regardless of viewing angle, while the same jug in the hologram in fig. 8 "takes up" different positions depending on the angle the hologram's plane forms with the direction of vision.

As indicated at the outset, autostereoscopy created with lenses over a flat screen exhibits per se known technology, fig. 11, to which there are fundamental functional/quality limitations, because known and traditional lens systems have so far not been able to provide an approximately satisfactory autostereoscopic experience in television, film or the like.

According to the invention, these limitations are lifted by inserting said specially designed microlenses to project all or parts of the vertical resolution on an LCD screen in the horizontal direction. If the entire vertical resolution is used in the horizontal direction, the number of unique angles in the horizontal direction will be squared, that is, 2x2 angles become 4x1 angles, 10x10 angles become 100x1 angles and so on.

Another limitation of autostereoscopic systems is linked to how large a viewing angle it is possible to achieve with a single lens. A lens normally has a curved focal plane, while the rear image elements usually lie in a completely flat plane, for example in an LCD screen, fig. 12. This means that only the image elements seen directly from the front will be correctly in focus, and this limits the viewing angle for the holographic image.

In optical engineering, this is a well-known problem, which can be solved by combining several lenses that flatten the focal plane, fig. 13. The disadvantage of such a solution is that the complexity of the systems increases and thus the price.

In accordance with the present invention, the complexity of the lens system is reduced without loss of viewing angle by - as previously described - projecting the image elements onto the curved focal plane of a single lens by means of the indicated microlenses. This results in a simple and inexpensive lens system without its usual limitation of a small angle of view.

Fig . 14A to 14C schematically illustrate light-shaping devices, here in the form of microlenses 10A, 10B and 10C, with mutually deviating designs.

In Fig. 14A, the microlens body is designed with curvature (without tilt) for focusing the light.

In Fig. 14B, the lens body 10B is designed with a slope (without curvature) for deflection of the light.

In Fig. 14C, the lens body is designed with both curvature and slope for focusing and deflecting the light.

In all three cases, curvature and/or inclination only occurs in one coordinate direction X, Y. If you want different deflection/inclination in the X and Y directions, the respective lens body 10A, 105 or 10C must be designed correspondingly, that is, with each other deviant slopes/curvature in the coordinate directions.

Claims (2)

1. Device for an automultiscopic screen that contains image elements arranged in lines and columns to form an image matrix, and an optical system which includes a first lens system comprising a lens element (10) for each image element (12, 14, 16, 18) in the image matrix, where the lens elements (10) are arranged in a lens matrix, a second lens system comprising macro lenses (20), a translucent diffuse film or screen plate which is placed between the lens systems, where the first lens system is arranged to project image elements from the image matrix on one side, the projection side, of the screen plate, so that a projected image matrix is formed there, and where the second lens system is arranged to display projected image elements that are visible on the opposite side, the display side, of the screen plate, characterized in that a group of lens elements (10) in the first lens system is arranged to project image elements (12, 14, 16, 18) from two or more lines in the image matrix to one line in the projected image matrix, so that the projected elements form a line segment (12a, 14a, 16a, 18a) on the projection side of the screen plate, and where sets of lens groups are coordinated to project elements as a column of line segments; and in that each macro lens in the second lens system is arranged to display at least one line segment which is visible on the display side of the screen plate. 2. Device for an automultiscopic screen according to claim 1, characterized in that the macrolenses have a curved focal plane and that the diffuse membrane/screen plate is positioned and curved so that the part of the display surface of the screen plate that is presented by a specific macrolens lies in the focal plane of the lenticular lens (2OA).